Can't install 64 bit OSs...

[RussB]

On one of the systems (a Windows 7 64 bit host) where I use VirtualBox, I am unable to configure/install any 64 bit versions of Windows. The 64 bit OS options do not even show up in the OS version drop-box. On the other system (a Windows 8.1 64 bit host) I have no problem installing them. (Both 32 and 64 bit OS versions show up in the drop-box.) Any idea why this is happening?

[loukingjr]

See: I have a 64bit host, but can't install 64bit guests